Exchangeable air-conditioning unit

ABSTRACT

An exchangeable air-conditioning unit ( 1 ) is described for attachment to mobile equipment. The air-conditioning unit includes a compressor ( 5 ) operable to compress a refrigerant and a hydraulic motor ( 17 ) operable to drive the compressor. Hydraulic fittings ( 11 ) are provided in fluid communication with the hydraulic motor for transporting hydraulic fluid. The hydraulic fittings ( 11 ) are adapted to be releasably connected to a hydraulic system of the mobile equipment. Refrigerant fittings ( 7 ) are provided in fluid communication with the compressor for transporting refrigerant. The refrigerant fittings ( 7 ) are adapted to be releasably connected to a refrigeration circuit of the mobile equipment. An enclosure ( 3 ) houses the compressor and hydraulic motor and has at least one releasable connector ( 21 ) for releasably connecting the enclosure to the mobile equipment. The exchangeable unit may be pre-charged with gas in and stored in readiness for attachment to the mobile equipment.

FIELD OF THE INVENTION

The present invention relates generally to air-conditioning systems and, in particular, to air-conditioning systems for use in mobile plant.

BACKGROUND OF THE INVENTION

Mobile plant such as haul trucks, loaders, dozers, shovels and draglines frequently operate in dirty or hazardous environments. Consequently, air-conditioning is generally required for the comfort and safety of personnel operating the mobile plant. The capital cost of the equipment may be large and there is a need to utilise the mobile plant productively, since the mobile plant may have a direct impact on the production capability of sites where the mobile plant is used.

Experience at a site using a fleet of twelve large trucks has shown that one of the trucks was effectively out of use at any one time due to air-conditioning issues. Maintenance of air-conditioning systems may require input from skilled technicians, who may not be immediately available when the mobile plant is operated in remote locations.

There is accordingly an on-going need to reduce the down-time of mobile plant due to maintenance issues.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an exchangeable air-conditioning unit for attachment to mobile equipment, the air-conditioning unit comprising:

a compressor operable to compress a refrigerant;

a hydraulic motor operable to drive said compressor;

hydraulic fittings in fluid communication with said hydraulic motor for transporting hydraulic fluid, wherein said hydraulic fittings are adapted to be releasably connected to a hydraulic system of the mobile equipment;

a first enclosure that houses said compressor and said hydraulic motor and has at least one releasable connector for releasably connecting the enclosure to the mobile equipment.

Preferably the air-conditioning unit comprises at least one refrigerant fitting in fluid communication with said compressor for conveying refrigerant, wherein said refrigerant fittings are adapted to be releasably connected to a refrigeration circuit of the mobile equipment.

In one arrangement, said air-conditioning unit further comprises a condenser arranged to receive compressed refrigerant from said compressor.

The air-conditioning unit may comprise a second refrigerant fitting in fluid communication with said condenser for conveying refrigerant, wherein said second refrigerant fitting is adapted to be connected to the refrigeration circuit of the mobile equipment.

The air-conditioning unit may further comprise an evaporator in fluid communication with said compressor and said condenser.

In one arrangement the air-conditioning unit comprises a second enclosure that houses said condenser and said evaporator.

The air-conditioning unit may comprise at least one quick-connect refrigerant fitting that, in use, provides fluid communication for refrigerant between the first housing and the second housing.

The air-conditioning unit may comprise a centrifugal fan operable to blow air past said condenser.

Preferably the at least one refrigerant fitting comprises:

-   -   a valve assembly having a plurality of valves that, when closed,         define a closed chamber within said valve assembly; and     -   a vacuum arrangement operable to remove refrigerant from the         closed chamber.

Preferably the valve assembly comprises a seal to limit the escape of refrigerant from the valve assembly.

Also described herein is a refrigerant fitting for releasably connecting a first section of a refrigerant circuit to a second section of the refrigerant circuit, the refrigerant fitting comprising:

-   -   a first valve having an open configuration in which a fluid         passage is provided for refrigerant flows between the first         section of the refrigerant circuit and the refrigerant fitting         and a closed configuration in which the first valve prevents         refrigerant flow between the first section of the refrigerant         circuit and the fitting;     -   a second valve having an open configuration in which a fluid         passage is provided for refrigerant flows between the second         section of the refrigerant circuit and the refrigerant fitting         and a closed configuration in which the second valve prevents         refrigerant flow between the second section of the refrigerant         circuit and the fitting;     -   a first part including said first valve;     -   a second part including said second valve; said first and second         parts having an assembled configuration wherein a chamber is         defined between said first valve and said second valve; and     -   a third valve formed between the chamber and a vacuum         arrangement wherein, in use, said first and second valves are         placed in the closed configuration and said third valve is         opened to enable the vacuum arrangement to draw refrigerant from         the chamber.

Preferably the refrigerant fitting comprises a sealing arrangement to provide a seal between the chamber and the atmosphere if said first part and said second part are in the assembled configuration.

Preferably said first part and said second part are shaped to provide mutually abutting surfaces if said first part and said second part are in the assembled configuration.

Preferably, said sealing arrangement comprises at least one O-ring.

Preferably, said refrigerant fitting comprises fastening means to hold said first part and said second parts in place in the assembled configuration.

According to a further aspect of the invention there is provided a method of separating a first section of a refrigeration circuit and a second section of the refrigeration circuit using the refrigerant fitting described above, the method comprising

-   -   closing said first valve and said second valve;     -   opening said third valve such that the vacuum arrangement draws         refrigerant from the chamber;     -   closing said third valve; and     -   separating said first part and said second part to thereby         separate the first and second sections of the refrigeration         circuit.

According to a further aspect of the invention there is provided a method of connecting a first section of a refrigeration circuit and a second section of the refrigeration circuit using the refrigerant fitting described above, the method comprising:

-   -   placing said first part and said second part in the assembled         configuration with said first, second and third valves in the         closed configuration;     -   opening said third valve such that the vacuum arrangement draws         air from the chamber;     -   closing said third valve; and     -   placing said first and second valves in the open configuration         to provide a fluid passageway between the first and second         sections of the refrigeration circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the drawings, in which:

FIG. 1A is a schematic diagram of a first embodiment of an exchangeable air-conditioning unit that includes a compressor and a hydraulic motor;

FIG. 1B is a schematic diagram showing an end view of the air-conditioning unit of FIG. 1A;

FIG. 2A is a schematic diagram of a second embodiment of the exchangeable air-conditioning unit that includes a condenser;

FIG. 2B is a cut-away end view of the air-conditioning unit of FIG. 2A;

FIG. 3A is a schematic diagram of a third embodiment of the exchangeable air-conditioning unit that includes an evaporator;

FIG. 3B is a cut-away end view of the air-conditioning unit of FIG. 3A;

FIG. 4A is a schematic diagram of a valve arrangement that may be used in the air-conditioning units of FIGS. 1A to 3B;

FIG. 4B is a schematic diagram of a male fitting for use in the valve assembly of FIG. 4A;

FIG. 4C is a schematic diagram of a female fitting that receives the male fitting of FIG. 4B;

FIG. 5A is a schematic diagram of a further embodiment of the exchangeable air-conditioning unit; and

FIG. 5B is a cut-away end view of the air-conditioning unit of FIG. 5A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1A shows an exchangeable air-conditioning unit 1 housed in an enclosure 3 that, in one arrangement, is made of stainless steel and is 60 cm in height and width and 20 cm deep.

The air-conditioning unit 1 includes an air compressor 5 driven by a hydraulic motor 17. An example of a suitable air compressor is the Unicla UP 200-4215™ and a suitable hydraulic motor is the Eaton 21301™ or the PLM Casappa 20-11.2 gear motor. The compressor 5 is connected to the motor 17 by a toothed rubber timing-belt 19. Alternatively the compressor 5 may be driven via a direct drive from the motor 17. Quick-connect refrigerant fittings 7 are provided on the enclosure 3, and refrigerant lines 9 transport refrigerant between the quick-connect refrigerant fittings 7 and the compressor 5. Examples of quick-connect refrigerant fittings that may be used are the Red Dot RD 2-0872-0P for the low-pressure side and the Red Dot RD-2-0871-0P on the high-pressure side.

In use, the quick-connect refrigerant fittings 7 are connected to piping (not shown) that leads to the remaining components of a refrigeration circuit, including a condenser and an evaporator, mounted elsewhere on the mobile plant on which the air-conditioning unit 1 is used. Mobile plant on which the air-conditioning unit 1 may be used includes, but is not limited to, mobile mining or earthmoving equipment, locomotives, cranes, tractors and harvesters.

The hydraulic motor 17 may be driven using the existing hydraulic system of the mobile plant. The enclosure 3 is provided with two quick-connect hydraulic fittings 11 and hydraulic lines 13 connect the hydraulic motor 17 to the hydraulic fittings 11. The flow of fluid through the hydraulic lines 13 is controlled by a solenoid-operated directional control valve (DCV) 15. The hydraulic circuit may include a flow control valve that is adjustable during commissioning to set the compressor speed. The hydraulic motor 17 may run at hydraulic pressures typically found in mobile plant, which are generally in the range of 2000-3000 psi. The air-conditioning unit may include a pressure relief valve to protect the hydraulic motor 17.

In use the hydraulic fittings 11 are connected to the hydraulic circuit of the mobile plant. In one arrangement Pirtek™ quick-connect hydraulic fittings are used.

FIG. 1B shows an end view of the enclosure 3, the refrigerant quick-connect fittings 7 and the hydraulic quick-connect fittings 11. The enclosure has quick-connect fasteners 21 that are used to attach the air-conditioning unit 1 to the mobile plant. The quick-connect fasteners 21 may be over-centre type clamps. The air-conditioning unit 1 may, for example, be attached to the outside of an operator's cabin in the mobile plant. The air-conditioning unit 1 may be disconnected and exchanged for a replacement unit in approximately 5 minutes without the need for specialised tools or the input of a specifically trained tradesperson.

The air-conditioning unit 1 may be tested and pre-charged with gas according to predefined specifications. A supply of ready-to-use air-conditioning units may then be kept at an appropriate location. If an air-conditioning unit currently attached to the mobile plant no longer works adequately, the unit may be replaced with a ready-to-use unit from the supply.

In operation, the compressor 5 may be driven by hydraulic pressure derived from the mobile plant's auxiliary hydraulic system. The hydraulic motor 17 runs continuously whilst a hydraulic pump (not shown) supplies hydraulic fluid via the hydraulic lines 13. The hydraulic motor 17 may be turned off by activating the solenoid-operated control valve 15.

FIG. 1A does not show the control wire connections to the DCV 15 and compressor 5. The enclosure 3 is provided with fittings that enable the control wires to be quickly connected to the air-conditioning unit 1.

The refrigerant circuit may be protected by both high pressure (HP) and low pressure (LP) safety switches. These safety switches shut down the unit 1 should their respective setpoints be reached. Indicator lamps are provided in unit 1 for both switches. The LP lamp is an alarm indicating a loss of system pressure. The HP lamp is for indication only and shows when the unit 1 has cycled off due to high pressure. Whilst the HP switch does offer system control, the primary temperature control may be a thermostat located in the cab. This may control both the solenoid of DCV 15 and the condenser fan.

The electrical box (not shown) located in the compressor housing 3 contains the necessary wiring and controls for the A/C system including circuit protection, relays and switches. A single 24v 30 amp supply from the main switch board of the mobile plant may enter the housing 3 and is distributed to the compressor 5, and DCV 15. In some arrangements the power is also supplied to a condenser and evaporator. Heavy duty Multipin IP64 rates plugs may be fitted to the compressor housing 3 to facilitate quick electrical connection and disconnection.

The compressor 5 may have a clutch (not shown) that is controlled by a thermostat switch dependent on temperature in a designated location, typically the operator's cabin. When the temperature in the cabin rises above a set level, the thermostat switch triggers, sending a control signal to engage the compressor clutch. The refrigerant is then circulated through the refrigeration circuit in a fashion similar to a standard automotive air conditioning system. Alternatively, the compressor 5 may be controlled by the thermostat operating the solenoid DCV 15.

The refrigerant exits the compressor 5 as a superheated vapour. Elsewhere in the circuit, a condenser removes heat from the vapour and causes the vapour to condense into a liquid. The liquid refrigerant then passes through an expansion valve that causes flash evaporation of the refrigerant. After the expansion valve, the refrigerant passes through an evaporator. Warm air, for example from the operator's cabin, is cooled by being blown across the evaporator. From the evaporator the refrigerant is returned to the compressor 5, completing the cycle.

FIG. 2A shows an exchangeable air-conditioning unit 100 that includes both a compressor and a condenser.

The air-conditioning unit 1 includes compressor 5, belt drive 19, hydraulic motor 17 and solenoid-operated directional-control-valve 15 that operate substantially as described with reference to FIG. 1A. In addition, the air-conditioning unit 100 includes a condenser 113 and a centrifugal fan 115 that blows air over the condenser 113 via ducting 117. The centrifugal fan 115 may also be driven by the belt drive 19. Alternatively, the fan 115 may be driven by a second hydraulic motor (not shown).

The hydraulic lines 13 and quick-connect fittings 11 are arranged in substantially the same way as in the air-conditioning unit 1. However, the refrigerant lines are arranged to accommodate the condenser 113. The refrigerant quick-connect fitting 7 b is connected to the compressor 5 by refrigerant line 9. Refrigerant flows from the compressor 5 to the condenser 113 via refrigerant line 111. From the condenser 113, refrigerant line 109 leads to the refrigerant quick-connect fitting 7 a. External refrigerant lines (not shown) convey the refrigerant from fitting 7 a to the expansion valve and the evaporator used to cool the air-conditioned space.

FIG. 2B shows a cut-away end view of the air-conditioning unit 100, sectioned along line A-A, and showing the fan 115, ducting 117 and condenser 113. The air-conditioning unit 100 may be housed in two enclosures 103, 130 which are preferably made of stainless steel. The enclosures 103, 130 have quick-connect fasteners 21 to attach the air-conditioning unit 100 to the mobile plant. The overall volume of enclosures 103 and 130 is generally larger than enclosure 3 to accommodate the condenser 113. In one configuration the enclosures measure 90×60×20 cm.

The compressor 5, hydraulic motor 17, DCV 15 and fan 115 are positioned in housing 130, and the condenser 113 is positioned in housing 103. A quick-connect refrigerant fitting is placed in line 111, enabling the housings 103, 130 to be separated. It is likely that the components in housing 130 will require maintenance more often than the condenser 103. Accordingly, housing 130 is likely to be detached and replaced more often than housing 103.

Alternatively, a single housing may be used instead of the two housings 103, 130.

FIG. 3A shows an air-conditioning unit 200 that includes a compressor, a condenser and an evaporator. The air-conditioning unit 200 has an enclosure 203 that contains compressor 5, drive belt 19, hydraulic motor 17, DCV 15, centrifugal fan 115 and condenser 113 configured substantially as described in the arrangement of FIG. 2A. In use, refrigerant flows from the compressor 5 to the condenser 113 through refrigerant line 211. From the condenser 113 the refrigerant flows to the evaporator 202 via refrigerant line 213. From the evaporator 202 there is a further refrigerant line (not shown) that returns the refrigerant to the compressor, completing the cycle. Thus, the entire refrigeration circuit is included in the air-conditioning unit 200 and there is no need for refrigerant quick-connect fittings 7.

Alternatively, the air-conditioning unit 200 may be housed in two separate modules. A module 230 contains the compressor 5 and hydraulic motor 17, and a second module includes the condenser 113 and evaporator 202. In this case quick-connect refrigerant fittings are used to connect refrigerant lines in the module 230 and the second module. Such an arrangement is illustrated in FIGS. 5A and 5B. A motivation for using the two modules is that the items in the module 230 (e.g. fan 115, compressor 5 and motor 17) are more likely to require servicing or replacement than the condenser and evaporator.

FIG. 3B shows a cut-away view of the enclosure 203 sectioned along line A-A. Evaporator 202 is mounted to an external surface of the enclosure 203. The quick-connect fasteners 21 are provided on the same external surface. When the air-conditioning unit 200 is attached to the mobile plant using fasteners 21, the evaporator 202 is positioned in a corresponding cavity in the mobile plant in or adjacent to the operator's cabin. Air may be cooled by being blown across the evaporator 202. The expansion valve is located adjacent to the inlet of evaporator 202.

One disadvantage of the exchangeable air-conditioning units shown in FIGS. 1A to 2B is that a small amount of refrigerant may escape while a unit is being connected or disconnected. FIGS. 4A to 4C show a valve assembly that may be used to limit the escape of refrigerant. The valve assembly 300 may optionally be used as the refrigerant quick-connect fitting 7.

The valve assembly 300 includes a female fitting 304, valves 314 and 318 and vacuum canister 320, which are all mounted on or within the enclosure 3,103,203 of the air-conditioning unit. A male fitting 302 connects to the external refrigerant lines and, during assembly, is fitted into the female fitting 304 of the valve assembly 300.

As most clearly seen in FIG. 4C, the female fitting 304 has a generally cylindrical shape, at one end of which the internal valve 310 is positioned. The end of the female fitting 304 opposite internal valve 310 is open to the atmosphere if male fitting 302 is not inserted. Captive nut 306 is provided at the open end of female fitting 304 and is arranged to receive a complementary threaded fitting 330 of the male fitting 302.

Two annular grooves are defined on an internal surface of the female fitting 304. An O-ring 308 is positioned in each of the grooves. When the male fitting 302 is inserted into the female fitting 304, a surface 332 of the male fitting 302 presses against the O-rings 308 to form a seal that prevents refrigerant from escaping between the male and female fittings.

From the internal valve 310 a refrigerant line 312 leads to the valve 314 that, in turn, connects to one of the refrigerant lines 9, 109 internal to the air-conditioning unit. The refrigerant line 312 has a side branch 316 that leads to valve 318 and vacuum canister 320. When the valve assembly is assembled, the lines 312 and 316 define a chamber within valve assembly 300 that may be isolated from the first (internal) and second (external) sections of the refrigeration circuit.

At one end of the male fitting 302 there is hole 336 that is sealed by the spring-operated non-return valve 334. The valve 334 includes a ball that is pressed against the housing of the male fitting 302 to seal the hole 336. When the male fitting 302 is positioned in the female fitting 304, a protruding portion of the internal valve 310 passes through the hole 336 and displaces the ball of valve 334 to create a passageway for the refrigerant to flow between the male fitting 302 and the female fitting 304.

The following procedure may be followed when a user disconnects the air-conditioning unit.

a) The user closes valve 314 to seal refrigerant within the air-conditioning unit. b) The user undoes nut 306 and partially retracts the male fitting 302. The spring-operated valve 334 then closes hole 336, sealing the refrigerant present in the external portion of the refrigeration circuit. In this step the male fitting 302 remains within the female fitting 304 and the O-rings 308 still provide a seal between the surface 332 and the female-fitting 304. At this stage a small volume of refrigerant is trapped in the refrigerant lines 312 and 316, which define a closed chamber. c) The user opens valve 318 and the trapped refrigerant in refrigerant line 312 is drawn into vacuum canister 320. d) Next, the user closes valve 318 and withdraws the male fitting 302 from the female fitting 304, completing the disconnection of the valve assembly 300.

To connect a new air-conditioning unit using the valve assembly 300, a user follows the following procedure.

i) The user inserts the male fitting 302 into the female fitting 304 until a shoulder of threaded portion 330 contacts the captive nut 306. In this configuration the O-rings 308 provide a seal between the female fitting 304 and the surface 332. The hole 336 is still sealed by the spring-operated valve 334 and thus refrigerant is still sealed in the external portion of the refrigerant circuit. ii) The user opens and then closes valve 318, removing air from the refrigerant line 312. iii) The user tightens captive nut 306. This has the effect of fixing the male fitting 302 in place within the female fitting 304 and also urges the male fitting against the internal valve 310. The internal valve 310 protrudes though hole 336, displacing the ball of valve 334 and creating a passage for refrigerant to flow into refrigerant line 312. iv) The user opens valve 314, permitting refrigerant to flow between refrigerant line 312 and refrigerant lines internal to the air-conditioning unit.

The vacuum canister may be evacuated via the quick-connect fittings, i.e. through the female fitting 304 with valve 318 open and valve 314 closed.

FIGS. 5A and 5B show a further embodiment 400 of the exchangeable air-conditioning unit. The unit 400 has a first housing 433 that contains the compressor and motor, and a second housing 435 that contains the condenser 113 and evaporator 202. It is likely that the contents of housing 433 will require replacement more frequently than the contents of housing 435.

The depicted air-conditioning unit 400 uses a combined hydraulic motor and compressor unit 405. Suitable direct-drive units are available from Red Dot Corporation. In operation, hydraulic fluid is pumped into housing 433 via quick-connect hydraulic fitting 11 a and hydraulic line 13. DCV 15 and flow control valve 407 are positioned in hydraulic line 13 to set the flow of hydraulic fluid. In use, a thermostat in the cabin of the mobile plant switches the hydraulic motor in unit 405 on and off by sending a signal to the solenoid-operated DCV 15.

From the combined motor/compressor 405, the hydraulic fluid flows via line 409 to hydraulic motor 415, which drives the centrifugal fan 115. From the motor 415, the hydraulic fluid flows out of the housing 433 via line 413 and quick-connect fitting 11 b.

The fan 115 draws air through air-intake duct 419 and blows the air through air-supply duct 427 into housing 435, where the blown air cools the condenser 113. An air-intake screen 417 may be placed in front of air-intake duct 419 to filter particles from the air. Fan 115 may supply air to both the condenser 113 and the evaporator 202. The fan 115 may be a twin-scroll type fan with independent air-flow to each coil. As an alternative, two independently-driven fans may be used.

The compressor in unit 405 compresses refrigerant, which flows via line 423 to quick-connect fitting 421 arranged between the housing 433 and 435 and enabling refrigerant to flow to condenser 113. From the condenser, line 429 transports the refrigerant to the evaporator 202. Air passing over the evaporator 202 may be used to cool air in the required portions of the mobile plant. From the evaporator 202, the refrigerant flows via a quick-connect fitting into refrigerant line 425 in housing 433 and is returned to the motor/compressor unit 405, completing the refrigeration cycle.

Air passing over the condenser 113 leaves the housing 435 via the condenser outflow screen 431.

The physical shape of housing 435 matches the configuration of the mobile plant such that the evaporator 202 is positioned to cool the required space within the mobile plant. The housing 435 and housing 433 have abutting surfaces accommodating the quick connect bulkhead fittings 421 that enable refrigerant to flow between the housings 433, 435. The abutting surfaces also accommodate airflow from the fan 115 through duct 427 into housing 435. One of the housings may have a rectangular hole that receives a complementary duct flange formed in the other housing.

In the drawings, like numerals are used to refer to similar features.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

It will also be understood that the term “comprises” (or its grammatical variants) as used in this specification is equivalent to the term “includes” and should not be taken as excluding the presence of other elements or features. 

1. An exchangeable air-conditioning unit for attachment to mobile equipment, the air-conditioning unit comprising: a compressor operable to compress a refrigerant; a hydraulic motor operable to drive said compressor; hydraulic fittings in fluid communication with said hydraulic motor for transporting hydraulic fluid, wherein said hydraulic fittings are adapted to be releasably connected to a hydraulic system of the mobile equipment; an enclosure that houses said compressor and said hydraulic motor and has at least one releasable connector for releasably connecting the enclosure to the mobile equipment.
 2. An exchangeable air-conditioning unit according to claim 1 wherein the air-conditioning unit comprises at least one refrigerant fitting in fluid communication with said compressor for conveying refrigerant, wherein said at least one refrigerant fitting is adapted to be releasably connected to a refrigeration circuit of the mobile equipment.
 3. An exchangeable air-conditioning unit according to claim 1 further comprising a condenser arranged to receive compressed refrigerant from said compressor.
 4. An exchangeable air-conditioning unit according to claim 3 comprising a second refrigerant fitting in fluid communication with said condenser for conveying refrigerant, wherein said second refrigerant fitting is adapted to be connected to the refrigeration circuit of the mobile equipment.
 5. An exchangeable air-conditioning unit according to claim 3 that further comprises an evaporator in fluid communication with said compressor and said condenser.
 6. An exchangeable air-conditioning unit according to claim 5 comprising a second enclosure that houses said condenser and said evaporator.
 7. An exchangeable air-conditioning unit according to claim 6 comprising at least one quick-connect refrigerant fitting that, in use, provides fluid communication for refrigerant between the enclosure and the second enclosure.
 8. An exchangeable air-conditioning unit according to claim 3 comprising a centrifugal fan operable to blow air past said 15 condenser.
 9. An exchangeable air-conditioning unit according to claim 2 wherein the at least one refrigerant fitting comprises: a valve assembly having a plurality of valves that, when closed, define a closed chamber within said valve assembly; and a vacuum arrangement operable to remove refrigerant from the closed chamber.
 10. An exchangeable air-conditioning unit according to claim 9 wherein the valve assembly comprises a seal to limit the escape of refrigerant from the valve assembly.
 11. An exchangeable air-conditioning unit according to claim 9 wherein said valve assembly comprises: a first valve having an open configuration in which a fluid passage is provided for refrigerant flows between the air-conditioning unit and the refrigerant fitting and a closed configuration in which the first valve prevents refrigerant flow between the air-conditioning unit and the fitting; a second valve having an open configuration in which a fluid passage is provided for refrigerant flows between the refrigeration circuit of the mobile equipment and the refrigerant fitting and a closed configuration in which the second valve prevents refrigerant flow between the refrigeration circuit and the fitting; a first part including said first valve; a second part including said second valve; said first and second parts having an assembled configuration wherein the chamber is defined between said first valve and said second valve; and a third valve formed between the chamber and a vacuum arrangement wherein, in use, said first and second valves are placed in the closed configuration and said third valve is opened to enable the vacuum arrangement to draw refrigerant from the chamber.
 12. An exchangeable air-conditioning unit according to claim 1, comprising flow control means to control a flow rate of the hydraulic fluid.
 13. An exchangeable air-conditioning unit according to claim 1 wherein the air-conditioning unit is pre-charged with refrigerant in readiness for attachment to the mobile equipment.
 14. A method of separating the compressor of the exchangeable air-conditioning unit of claim 11 from the refrigeration circuit of the mobile equipment with which the air-conditioning unit is used, the method comprising closing said first valve and said second valve; opening said third valve such that the vacuum arrangement draws refrigerant from the chamber; closing said third valve; and separating said first part and said second part to thereby separate the compressor and the refrigeration circuit.
 15. A method of connecting the compressor of the exchangeable air-conditioning unit of claim 11 to the refrigeration circuit of the mobile equipment with which the air-conditioning unit is used, the method comprising: placing said first part and said second part in the assembled configuration with said first, second and third valves in the closed configuration; opening said third valve such that the vacuum arrangement draws air from the chamber; closing said third valve; and placing said first and second valves in the open configuration to provide a fluid passageway between the compressor and the refrigeration circuit.
 16. Mobile equipment comprising the exchangeable air-conditioning unit of claim
 1. 17. Mobile equipment configured to receive the exchangeable air-conditioning unit of claim 1, comprising: a cooling circuit arranged to cooperate with the compressor of the air-conditioning unit; quick-release refrigerant fittings operable to provide fluid communication of refrigerant between the compressor and the cooling circuit; quick-release hydraulic fittings operable to provide fluid communication of hydraulic fluid between the hydraulic motor of the air-conditioning unit and a hydraulic system of the mobile equipment; and at least one releasable connector arranged to releasably connect the housing to the mobile equipment.
 18. A method of attaching an exchangeable air-conditioning unit to mobile equipment, comprising: providing the air-conditioning unit comprising an enclosure comprising a compressor operable to compress a refrigerant and a hydraulic motor operable to drive the compressor; attaching the enclosure releasably to the mobile equipment using at least one releasable connector; attaching quick-release hydraulic fittings to provide fluid communication of hydraulic fluid between the hydraulic motor and a hydraulic system of the mobile equipment; and attaching quick-release refrigerant fittings to provide fluid communication of refrigerant between the compressor and a cooling circuit of the mobile equipment.
 19. A method of attaching an exchangeable air-conditioning unit to mobile equipment as claimed in claim 18, comprising: pre-charging the air-conditioning unit with refrigerant in readiness for attachment to the mobile equipment. 